Project 3 PROJECT SUMMARY A high prevalence of CMV seropositivity in both organ donors and organ recipients makes CMV reactivation following transplantation a significant cause for morbidity and mortality and a contributor to poor graft outcome. An emerging concept in CMV reactivation points to transplant-induced inflammation as an early trigger for CMV transcriptional reactivation. Administration of immunosuppressants further suppresses viral-specific immunity, leading to the eventual completion of lytic viral replication. We hypothesize that achieving robust donor-specific transplant tolerance will inhibit transplant-associated inflammation, therefore remove a critical early trigger for epigenetic reprogramming and transcriptional reactivation of the CMV viral genome, and consequently prevent CMV reactivation. We propose to test this hypothesis in a forward-thinking, highly clinically relevant donor-specific transplant tolerance model using a strategy of pre-transplant donor ?negative vaccination? by delivery of donor cells treated with the chemical crosslinker 1-ethyl-3-(3-dimethylaminopropyl)- carbodiimide (ECDI). Our studies in murine models of transplantation tolerance have already led to ongoing pre-clinical studies in non-human primate models of allogeneic and xenogeneic transplantation. Moreover, a first-in-human clinical trial based on the same principle using peptide-coupled autologous cells in patients with multiple sclerosis recently established the clinical feasibility, tolerability, and safety of this novel tolerance strategy. Our preliminary data using MCMV demonstrated that tolerance by this approach prevented immediate early (IE) gene transcriptional reactivation from latent MCMV. Conversely, acute MCMV infection impaired attempted tolerance induction and destabilized established tolerance. Therefore, in the current application (Project 3), we propose to examine the following three areas using murine transplant models with MCMV infection and ECDI-donor cell tolerance strategy: (1) the effects of donor-specific tolerance on MCMV acute infection, establishment of latency, and reactivation from latency; (2) the effects of MCMV infection on the induction and stability of donor-specific tolerance; (3) the cellular mechanisms underlying the reciprocal interactions between MCMV infection and donor-specific tolerance. Our long-term goal is to determine therapeutic targets for prevention of CMV reactivation while establishing and maintaining stable donor-specific transplant tolerance.